Hi there!
I have been trying to get an Arduino project which involves a RF module, an ArduCAM, a gps and an SD card module. I have been using the third party Iduino Due for this project. I am able to send commands to the Iduino via RF to take pictures and perform other functions. The problem I am having however is that the SD card storage does not work unless the serial monitor is open. I know this because I am able to receive error messages via RF. When I have the iduino connected to the computer and a serial monitor (even a putty monitor for that matter) open, the SD card is recognized and the program works perfectly. I was wondering about the cause behind this as the SD card module (on the SPI bus) should not be influenced by the serial monitor. The camera, which also utilises SPI, does get recognized.
I have added delays before initialising the SD system and tried pulling down my Rx and Tx to ground but to no avail as the situation stays the same - the SD card module works if the serial monitor is open. THe rest of the program is not influenced by the serial monitor and works fine.